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1879.] PROF. J. R. GREENE ON A RARE MEDUSA. 797 We may now trace the attempts of successive zoologists to inter­pret Charybdeidee. Linnseus records the species of Plancus in the Systema Naturae (ed. xii. p. 1097)1 as Medusa marsupialis. H e is followed by Gmelin2 and Modeer3. In 1809 Pe'ron and Lesueur found the genus Carybdea. It in­cludes their new species (C.periphylla) together with that of Plancus. Lamarck4, Cuvier5, Goldfuss6, Schweigger7, the editors of the Ency­clopedic Me'thodique8 and Latreille9, accept the new genus. Eschscholtz does not cite Peron's new species or genus. He refers the species of Plancus to Oceania as O. marsupialis10. Milne-Edwards suggests the affinity of C. marsupialis to C. alata, Eeynaud, and Bursarius cythereee, Lesson. De Blainville11 retains the genus of Pe'ron, and gives in his Atlas the first copy of Lesueur's previously unpublished figure of C. peri-phylla. Coloured figures of this species (likewise copied from Lesueur's drawing) and of C. marsupialis (original) are added by Milne-Edwards to the large illustrated edition of ' Le Regne Animal."' Lesson12 is the first to break up the genus of Peron. His Carybdea includes C. periphylla, while the species of Plancus is referred (as M. planci) to the new genus Marsupialis. This procedure is sub­sequently sanctioned by Agassiz. Lesson proposes tbe two tribes of found at Eomblon a fifth species with very peculiar genitalia. Each of these does not, as in other Charybdeidae, form a continuous lamina freely projecting into its lateral pouch. The genitalia are constituted rather by the modified walls of diverticula from the pouches. They form, when mature, branched arbuscules, reaching far into the interior of the disk itself and splinted by processes of its gelatinous substance. In the lumen between these processes and their investing inner membrane [endoderm] the sexual products are developed. Semper further notes a small acaleph, likewise velate and probably charyb-deoid, with very complex marginal bodies. In this connexion he declares it unnatural to insist on establishing two primary groups of discoid Medusa? after the manner of Eschscholtz and his successors. Such divisions, based on single characters, arise from the delusive desire to thrust a straight-jacket of man's device upon the free creations of nature (Keisebericht, 1864). 1 Tom. i. pars ii. (1767). Also ed. x. torn. i. p. 660 (1760). 2 Syst. Nat. p. 3154. 3 Whose work I have not seen. I take this reference from Eschscholtz. 4 Hist. nat. des animaux sans vertebres, tome ii. p. 496 (1816). & Le Begne animal, tome iv. p. 59. " Lorsque ces animaux si simples prennent plus de concavite, leur surface inferieure devient interieure, et peut etre regardee comme un veritable estomac. Ce sont les CARYBDEES, Per. Ceux ou Ton ne voit a l'interieur aucunes traces de vaisseaux, ne different proprement des hydres que par la grandeur." 1817. 6 Handbuch der Zoologie, erste Abtheilung, p. Ill (1820). 7 Handbuch der Naturgeschichte der skelettlosen ungegliederten Thiere, p. 500 (1820). 8 Histoire naturelle des Zoophytes ou Animaux Eayonnes, faisant suite a l'Histoire naturelle des Vers de Bruguiere; par M M . Lamouroux, Bory de Saint- Vincent et Eud. Deslongchamps, tome ii. p. 165 (1824). 9 Families naturelles du regne animal, p. 540 (1825). 10 System der Acalephen, p. 101 (1829). De Blainville carelessly states that Eschscholtz places this species in Mquorea. , , , .;oa., 11 Manuel d'Actinologie, p. 275, and Atlas, pi. xxxi. f. 1 (1»34). 12 Prodrome (1837); Histoire naturelle des Zoophytes-Acalephes (1843).